Estimating the submarine groundwater and nutrients discharge of Yellow River delta with cross-section method

In this paper, cross-section method was used to estimate the groundwater and nutrients discharge fluxing to the Bohai Sea from the Yellow River Delta. The flux of shallow phreatic groundwater (within 10 m) in the Yellow River Farm discharging into sea was 2.9 × 10⁻⁵ m³/m d in 2004 and 3.1 × 10⁻⁵ m³/m d in 2005. Time distribution monthly mean flux is consistent with the Yellow River's runoff but taking on lag effect. And the volume of the phreatic water discharging from the whole delta is 3.71–3.77 × 10³ m³, which is 2 × 10⁻⁵% of the Yellow River's annual runoff. The transport amount of shallow confined water (buried depth 15–20 m) from 2004 to 2005 was 5.7–6.2 × 10⁻³ m³/m d in the Yellow River delta, 0.0037–0.004% of the runoff of Yellow River. There is low concentration of NO₃⁻, NH₄⁺ and PO₄³⁻ but high dissolved SiO₂ in the shallow confined aquifer. Despite the high concentration of phreatic nitrate, it weakly influences the seawater because of the little flux of discharge into sea.